R2 Highway Efficiency Test: 80 MPH vs 70 MPH Changed Everything

[mkhuffman]

What debate?

Where does that data come from, how does it mean anything when you don't provide any context?

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[ksurfier]

Where does that data come from, how does it mean anything when you don't provide any context?

At 70 mph, aerodynamic drag is one of the largest energy demands, so CdA does a surprisingly good job of predicting the relative highway efficiency of the Model Y, R2 and R1S.

As CdA increases, miles per kWh generally decreases. For example, the R2 has about 32% more CdA than the Model Y, so it must use substantially more energy to push air at the same speed. The R2 also has about 13% less CdA than the R1S, helping explain why it should be more efficient.

To make a meaningful comparison, however, the vehicles must be evaluated under similar conditions. Speed, elevation, temperature, wind, road grade, tires, climate-control use and vehicle load can all materially affect efficiency. Ideally, comparisons should be normalized to the same speed, temperature, elevation and still-air conditions so that differences in mi/kWh are more likely to reflect the vehicles themselves rather than the test environment.

 

[mkhuffman]

At 70 mph, aerodynamic drag is one of the largest energy demands, so CdA does a surprisingly good job of predicting the relative highway efficiency of the Model Y, R2 and R1S.

As CdA increases, miles per kWh generally decreases. For example, the R2 has about 32% more CdA than the Model Y, so it must use substantially more energy to push air at the same speed. The R2 also has about 13% less CdA than the R1S, helping explain why it should be more efficient.

To make a meaningful comparison, however, the vehicles must be evaluated under similar conditions. Speed, elevation, temperature, wind, road grade, tires, climate-control use and vehicle load can all materially affect efficiency. Ideally, comparisons should be normalized to the same speed, temperature, elevation and still-air conditions so that differences in mi/kWh are more likely to reflect the vehicles themselves rather than the test environment.

Thank you, AI bot. But you didn't answer my question.

 

[ohmman]

FWIW, my 2022 Model Y with 76k miles on it, the majority of which are going between my home in Sonoma (220ft above sea level) and Truckee, CA (6545ft above sea level) with LOTS of snow/cold driving, has averaged 265Wh/mi or 3.77mi/kWh. I certainly don't expect the same performance from my R2 but I disagree overall with suggestions that the MY gets 3mi/kWh at 70mph in ideal conditions. I drive on I-80 with everyone else, meaning I'm going 79-84mph most of the time.

I understand this is an aggregate number, but I can run an analysis on my next roundtrip up/back and see where I land.

 

[blipit]

What debate?

OOS just posted new MY Perf 10% challenge.

It got 3.3 mpk at 80mph.

 

[ksurfier]

OOS just posted new MY Perf 10% challenge.

It got 3.3 mpk at 80mph.

That 3.3 mi/kWh at 80 mph reinforces the key difference the EPA numbers miss. At lower highway speeds, the R2 and Model Y may have similar usable 10–70% road-trip range, but the Model Y holds its efficiency much better as speed rises (~30% lower drag than R2).

Model Y Performance would still provide at least 130 miles between 10% and 70%, while the R2 may be closer to 100 (or less) miles. The additional high-speed range can affect charger selection, stop frequency, and overall trip time; especially on routes with wider charger spacing.

 

[Budman]

Ya but. Can you do this with a Model Y???

 

[Apprunner]

OOS just posted new MY Perf 10% challenge.

It got 3.3 mpk at 80mph.

Yeah...not surprising. I was hoping R2 would have more mileage than my Model 3 given its bigger battery but the boxy shape will probably be noticeably less for roadtrips. 70mph is not practical for California road trips so the 80mph is a much better indicator. I'm hoping the R2 gets at least 2.7 mpk then at least its getting near 150 miles of range for a 10-70% charge.

 

[ksurfier]

Look forward to seeing your results...here's a general idea of what you might expect to see...pretty steep drop off from 63 mph to 82 mph:

MPK	Range	Speed
3.6	315	57.0
3.4	300	60.0
3.3	290	63.0
3.1	275	66.5
3.0	264	67.0
2.9	251	70.0
2.8	250	71.0
2.7	238	74.0
2.6	225	76.5
2.4	212	79.0
2.3	200	82.0

 

[dscoti]

Boy, the testosterone is flowing in this thread. Reminds me of two Chihuahuas in a standoff 10’ apart.

 

[mkhuffman]

Look forward to seeing your results...here's a general idea of what you might expect to see...pretty steep drop off from 63 mph to 82 mph:
MPKRangeSpeed3.631557.03.430060.03.329063.03.127566.53.026467.02.925170.02.825071.02.723874.02.622576.52.421279.02.320082.0

The efficiency of the R2 is 2.6 mi/kWh at 79 mph.

 

[ksurfier]

The efficiency of the R2 is 2.6 mi/kWh at 79 mph.

I was seeing less than 2.0 MPK on my own highway test drive, so I have a hard time believing 2.6 MPK at 79 mph in still air is realistic. Even allowing for heavy A/C use, climate control would not explain a 0.6 mi/kWh difference by itself. The only first-hand report near 2.6 MPK also benefited from a 5–10 mph tailwind, so it does not support using 2.6 mi/kWh as a normalized 79 mph benchmark.

 

[Indy avocado]

That 3.3 mi/kWh at 80 mph reinforces the key difference the EPA numbers miss. At lower highway speeds, the R2 and Model Y may have similar usable 10–70% road-trip range, but the Model Y holds its efficiency much better as speed rises (~30% lower drag than R2).

Model Y Performance would still provide at least 130 miles between 10% and 70%, while the R2 may be closer to 100 (or less) miles. The additional high-speed range can affect charger selection, stop frequency, and overall trip time; especially on routes with wider charger spacing.

Look forward to seeing your results...here's a general idea of what you might expect to see...pretty steep drop off from 63 mph to 82 mph:

MPK	Range	Speed
3.6	315	57.0
3.4	300	60.0
3.3	290	63.0
3.1	275	66.5
3.0	264	67.0
2.9	251	70.0
2.8	250	71.0
2.7	238	74.0
2.6	225	76.5
2.4	212	79.0
2.3	200	82.0

Not wrong that Model Y Performance punches above EPA here.

I have no way to prove or disprove this table of speeds and ranges. 70mph looks reasonable. Would be nice if you shared method and sources.

I just added the 10% challenge data to my calculator and added some additional corrections and features. Both Model Y performance range tests I have punch above the expected performance. R2 and Model Y Premium hit their marks.

 

[BigE]

When explaining mileage and range to our non-EV friends, it often helps to put things in ICE vehicle terms.

Example: depending on which R2 variant you end up with, an 88 kWh usable pack ÷ 33.7 kWh of energy per gallon of gasoline ≈ 2.6 gallons of fuel in an R2. My R1T Max pack is roughly 4.2 gallons equivalent.

My point is, when you look at how few gallons of “fuel” you actually have, it becomes much more apparent why wind, temperature, speed, etc. have such a noticeable impact on range. Those factors eat a much bigger percentage of a 3-gallon tank than they do of a 15–20 gallon tank.

 

[mkhuffman]

... Would be nice if you shared method and sources.

His method and sources are the same as mine: wild ass guess, not taking into account anything other than speed.

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